One might say that the rabbit hole that is the AR platform is an endless, procedurally generated maze of history, details, variations, and contentious debate, and when I tip toed (roguelike, naturally) into that cave the default, go-to calibers of ammunition used with the AR were the 5.56 NATO and .223 Remington. Wander past the vestibule and you’ll likely hear about the .300 AAC Blackout, the relatively recent upstart that inspired an army of followers and an opposing army of aspersionates (if that isn’t a word, then it should be). The story of the Blackout cartridge is worth reading in its abbreviated form, courtesy of Wikipedia, and I’ll leave that background referenced like that for now.
Joining the .300 Club
The AR platform has evolved to be a mind-bogglingly flexible one that accommodates a myriad of calibers, so looking at the Blackout as a nearby stepping stone seemed an easy way to go beyond the 5.56/.223 default. Thanks to Palmetto State Armory and their frequent “ding & dent discount” of “blemished” AR components, I was able to source complete upper and lower assemblies for a .300 Blackout pistol for about $450, although when you add in the optic, bolt carrier group, and some other gee-gaws the total project cost rises dramatically.
One Upper and Two Lowers
Proof that persistent marketing e-mails do work, here’s two AR pistol lowers that I ordered from PSA. Matched with each lower is the same Blackout upper with a Sig Sauer Romeo 5 red dot (and an O-Light flashlight/laser combo that eventually got installed elsewhere). The M-LOK QD sling attachment was purchased at a nearby gun shop, while the sling was an Amazon tacticool special. As was the foam “bike handle” buffer tube pad.
To the Range
I took all three assemblies to the PSTC gun range to test them out. An immediate discovery was that the “foamy” lower - the one with the buffer tube pad - would not feed a round from a magazine. After some consternation, I realized that the added diameter around the buffer tube interfered with the charging handle and thus resulted in said consternation. Which was kind of odd considering that this lower assembly worked fine with a 5.56 pistol upper, but anyway, switching to the other “braced” lower (i.e., the one with the stablizing brace) got things working fine.
Two things I’d noticed about the .300 AAC Blackout cartridge: 1) it’s more expensive than and not as available as the 5.56 or .223 and 2) it’s got a sharper kick than the .223 or 5.56. Thanks to the doubled-up hearing protection of earplugs and muffs I couldn’t tell if the Blackout was any louder, and I noticed a lack of a fireball which might have been a function of the cartridge as well as the flash can installed on the barrel.
Getting to Zero
I’ve seen folks deck out their AR pistols with magnified optics, backup sights, forward hand grips, folding buffer tubes, and so on, but I wanted to keep things as simple as possible which meant basically a single red dot. After a few iterations of shooting and adjusting, I got reasonably close on a 6" bullseye target at 25 yards, all shots fired from an unsupported, standing position.
As ammo supplies were limited, I had to make the most of what I had on hand, but I had enough cartridges to try a human-sized target and a scaled down Appleseed-style silhouette at 25 yards. Not going to be winning any marksmanship matches with these results, but I’m okay with them.
So, much noise and many holes were made that night.
Got to Keep ‘Em Separated
One bit of important housekeeping is that while (or perhaps because) magazines and bolt carrier groups are interchangeable between 5.56/.223 and .300, the barrels and chambers definitely are not and can lead to catastrophic (i.e., deadly) failures (i.e., explosions) if mismatched. Which means that careful labeling and separation of these calibers is absolutely essential.
Crappy paint penmanship, while perhaps avoidable, is a regrettable part of the experience.
A Hobby Horse Minus the Horse
Given the shortage of ammunition these days, jumping on the Blackout bandwagon might not have been the best idea, but given how infrequently I foresee taking this firearm to the range, the experience and discovery of thinkering with a new (to me) caliber and configuration definitely are worth it.